Packagings of this kind are used for the packaging of usually solid items, but also of soft, possibly flowable, items. They are wrapped in a rectangular or square film blank, there thus being formed a longitudinal edge opposite the wrapping edge and two transverse edges extending between that edge and the wrapping edge. The latter edges and the longitudinal edge are sealed to one another to form a longitudinal and two transverse sealed seams, so that the item is securely packaged and protected from environmental influences. The transverse sealed seams generally extend directly along the transverse edges, that is to say the lateral boundary of the packaging, while the longitudinal sealed seam is spaced apart from the associated longitudinal edge. It is thus possible to open the packaging relatively conveniently from the longitudinal edge side. It is merely necessary to separate the two longitudinal edge strips, which are each defined by the longitudinal sealed seam and the longitudinal edge and which are in direct contact with one another, by means of two thumbs or two fingers and then to hold each of them firmly between thumb and finger. The two longitudinal edge strips can then be pulled apart to open the longitudinal sealed seam. In order to facilitate separation of the two longitudinal edge strips, one of the longitudinal edge strips is very slightly broader than the other longitudinal edge strip, so that the one longitudinal edge strip projects very slightly beyond the other longitudinal edge strip, preferably by about 1 to 2 mm.
A disadvantage of such known packagings, however, is that the user cannot easily see whether or not the packaging has already been opened either by himself or by a third party. This is the case especially when the packaging is a resealable packaging, more especially a packaging in which at least a portion of the longitudinal sealed seam, especially both the longitudinal sealed seam and the two transverse sealed seams, are formed by cold-seal adhesive strips that are in contact with one another and are capable of being restuck a number of times. Such packagings can easily be opened and resealed without it being evident to a subsequent purchaser.
The problem underlying the present invention is therefore to produce a packaging that provides reliable evidence of being opened for the first time.
This problem is solved by the characterising features of claim 1, preferred structural details and embodiments being described in the subsidiary claims.
A key feature of the invention is therefore that at at least one point between the longitudinal sealed seam and the longitudinal edge there is arranged a device for indicating whether the packaging has already been opened, that is to say a so-called “seal guarantee”. It will be understood that such quality seals can also be provided in the region of the transverse sealed seams, especially when they are also capable of being resealed.
A particularly simple embodiment of a device for indicating whether a packaging has already been opened, especially one that is also simple from the production technology standpoint, is characterized in that there is arranged on the inner side of one of the two longitudinal edge strips a so-called adhesive tag (circular, oval, rectangular or the like) which is associated with a colour marking on the inner side of the other, or opposite, longitudinal edge strip, wherein, on detachment of the adhesive tag from that colour marking, colorant remains clearly visibly adhering to the adhesive tag. If, therefore, the two longitudinal edge strips are manipulated for the purposes of opening, this will be clearly evident to the purchaser of the packaging. It is necessary merely to check whether or not the adhesive tag has been coloured. Such an adhesive tag is preferably not capable of being restuck.
The colorant which serves for marking the adhesive tag when the packaging is opened is preferably applied directly to a film forming the film packaging and/or to a suitable film laminate on the adhesive side of the film or the laminate, for example by means of gravure printing.
It should be noted in connection with the cold-seal adhesive used herein that it preferably consists of an acrylic-based material and, at least in the region of the longitudinal sealed seam, is capable of being restuck at least three times, especially up to 10 to 15 times, without the closure strength being appreciably affected.
The cold-seal adhesive has especially been produced on the basis of a water-based styrene-acrylate dispersion and is such that on each closing or re-sticking operation it has a closure strength having at least 50% to 80% of the preceding closure strength.
According to the invention the initial closure strength of the cold-seal adhesive is in the range of from 3.2 N/15 mm to 2.5 N/15 mm, preferably in the range of from 3.0 N/15 mm to 2.65 N/15 mm and more especially in the range of from 2.75 N/15 mm to 2.85 N/15 mm.
On the basis of such an initial closure strength, multiple re-sticking by means of which the packaging is securely closed after resealing can advantageously be realised in a simple way.
According to the invention, the cold-seal adhesive has a solids content in the range of from 40% to 65%, preferably in the range of from 45% to 60% and more especially in the range of from 50% to 53%. The viscosity of the cold-seal adhesive at 25° C. is in the range of from 350 cp to 650 cp, preferably in the range of from 400 cp to 580 cp and more especially in the range of from 480 cp to 520 cp, the viscosity being determined in accordance with Brookfield ASTM D3236.
Furthermore, the application weight of the cold-seal adhesive is in the range of from 3.8 g/m2 to 5.2 g/m2, preferably in the range of from 4.2 g/m2 to 4.8 g/m2 and more especially in the range of from 4.35 g/m2 to 4.55 g/m2.
The colorant used for marking the adhesive tag is water-based and has a solids content in the range of from 28% to 42%, preferably in the range of from 32% to 38% and more especially in the range of from 33% to 34.5%, the colorant having a viscosity at 20° C. in the range of from 75″±10″ B6 cup, preferably 75″±5″ B6 cup (corresponds to 805 cp±53.13 cp according to Brookfield ASTM D3236).
The application dry weight of the colorant is in the range of from 0.25 g/m2 to 2.8 g/m2, preferably in the range of from 0.8 g/m2 to 1.8 g/m2 and especially in the range of from 1.0 g/m2 to 1.5 g/m2.
When the above-mentioned parameters are observed, a seal guarantee according to the invention by means of an adhesive tag and a colour marking associated therewith can be produced without problems. Such a seal guarantee is accordingly capable of being produced in an extremely simple way, it being possible to use a very wide range of printing technologies and special preference being given to flexographic and/or gravure printing, because both the above-defined colorant(s) and the above-defined cold-seal adhesive are suitable for flexographic and/or gravure printing.
In accordance with a practical embodiment, the colorant used is applied by means of a printer unit directly to the acrylic side of a film, for example a film of an oriented polypropylene, the adhesive strength between the film and the colorant applied thereto being relatively low and tending towards 0 N/15 mm, but still being sufficiently high that the colorant has adequate resistance to abrasion and to breakage and remains securely on the film until the packaging is stuck together, i.e. closed.
Following the application of the colorant to the film, the film including the colorant is overprinted with a cold-seal adhesive, the adhesive strength between the film and the cold-seal adhesive being greater than the adhesive strength between the colorant layer underneath the cold-seal adhesive and the film.
The functioning of the seal guarantee, or the adhesive tag, is based on the fact that for sealing the packaging the longitudinal sealed seams of the packaging, which are coated with cold-seal adhesive, are brought together so that two cold-seal adhesive layers or a cold-seal adhesive layer and a film layer come into contact, so that the packaging is closed by all-round adhesion, that is to say from wrapping edge to wrapping edge.
The resulting layer structure is accordingly as follows: film/cold-seal adhesive=cold-seal adhesive/colorant/film or alternatively film=cold-seal adhesive/colorant/film. Accordingly the “=” reflects the point in the layer structure that provides for sealing the film packaging, that is to say the adhesive bond between the two longitudinal edge strips.
As a result of the afore-mentioned relatively weak adhesive strength between the colorant layer and the film in comparison with the adhesive strength between the cold-seal adhesive and the film, when that seal is opened the colorant layer remains adhering to the adhesive in the region of the adhesive tag and is at least partly torn or detached from the film therewith, so that after the packaging has been opened the adhesive tag is coloured by the colorant. Accordingly, when the packaging is opened the seal is broken in the region of the adhesive tag not in a reverse procedure with respect to the procedure used for sealing the packaging, wherein two cold-seal adhesive layers or a cold-seal adhesive layer and a film are brought into contact, but is broken at the weakest point of the layer structure formed, or defined, by the bond between the colorant and the film.
It should be mentioned at this point that the film for the production of the film packaging according to the invention can be in the form of a standard film or in the form of a film laminate. If desired, the laminate is provided with a metal layer and is preferably in the form of an aluminium laminate which has at least one sealing layer and optionally a barrier layer, for example of SiO2, ethyl vinyl alcohol (EVOH) or an oriented polyolefin, especially polypropylene (OPP). Furthermore, the oriented polyolefin is preferably unidirectionally stretched.
As an alternative to the above-mentioned device for indicating whether a packaging has already been opened, it can be defined by an adhesion or sealing point, the sealing point being bounded by tear-lines at least on one of the two longitudinal edge strips so that when the packaging is opened for the first time a correspondingly bounded edge strip portion is visibly separated together with the sealing point. The longitudinal edge strip in question is then visibly destroyed after the packaging has been opened for the first time. In that respect, the user is provided with a seal guarantee similar to that provided by a quality ring on the screw closure of a bottle of mineral water.
Preferably, a plurality of devices for indicating whether the packaging has already been opened are located, spaced apart from one another, in the region of the longitudinal edge strips that are in contact with one another, the spacing between the devices being such that if an opening is made between them there is insufficient space to gain access to the contents of the packaging.
Further embodiments of the invention will be found in the subsidiary claims.